Prolactin (PRL) is a clinically important pituitary hormone and neuropeptide which has been implicated in the expression of a variety of vertebrate behavior patterns. In the vast majority of cases, however, the specificity and site(s) of PRL action, and the relationship between PRL dose and behavioral response remain unknown. Accordingly, the proposed research would characterize in detail the relationship between PRL and several different PRL-sensitive behaviors in a single species, the ring dove (Streptopelia risoria). This species is ideally suited for these studies because: 1) there is more evidence for the existence of PRL-dependent behavior patterns in the ring dove than in other vertebrates, and 2) there is evidence for both central and peripheral sites of action of PRL in promoting various behavior changes in this species. Three PRL-dependent behaviors would be explored. 1) PRL-induced ingestive behavior: The time course, dose-response properties and specificity of PRL's centrally mediated action on food and water intake would be characterized following intracerebroventricular (ICV) injection of purified ovine PRL. To provide a neuroendocrine correlate of PRL's behavioral actions, parallel studies would be conducted on PRL-induced suppression of gonadotropin secretion, which also appears to be centrally mediated. 2) PRL-induced parental behavior: The effects of ICV injections of PRL on parental behavior in non-breeding doves would be tested to determine whether the increase in parental behavior which is observed following systemic injection of the hormone is due to a direct action of PRL on the brain or to effects on peripheral target organs. 3) PRL effects on incubation behavior: A study would be conducted to determine if subcutaneous PRL injections can prevent the decline and early termination of sitting activity which normally occurs in doves which are separated from their mates during the early incubation period. Clarification of PRL's role in maintaining ongoing incubation will help to interpret previous findings that PRL maintains readiness to incubate in nest-deprived doves. Collectively, the proposed experiments would contribute significantly towards an understanding of the behavioral and neuroendocrine pathology of hyperprolactinemia in men and women and should further our knowledge of the mechanism of neuroleptic drug action. These results will also help in formulating general principles of neuropeptide and protein hormone action on behavior.